Field of the Invention
This invention relates to constant velocity ratio universal joints of the kind comprising a hollow outer member and an inner member, provided with pairs of opposed longitudinally extending grooves, a plurality of balls disposed one in each of said pairs of grooves for torque transmission between said members and movable along said grooves to permit relative angular and axial (plunging) movement between said members, and a cage disposed between the inner and outer joint members and having apertures in which said balls are received, said cage having part-spherical inner and outer surfaces which co-operate with respective surfaces associated with the inner and outer joint members so that the balls are maintained in a plane bisecting the angle between the rotary axes of the joint members to impart the required constant velocity ratio characteristics to the joint. Such a universal joint will hereafter be referred to as a universal joint of the kind specified.
One disadvantage of universal joints of the kind specified is that the balls can skid along the grooves in one or both joint members during plunge, rather than rolling along the grooves. Skidding of the balls produces an undesirably high friction resistence to plunge. If skidding is to be avoided, the cage (which is slidable axially of the outer joint member) is required to be slidable relative to the inner joint member by a distance equal to half the total permitted plunging movement of the joint, and in one construction proposed hitherto this has been achieved by having the inner part-spherical surface of the cage engage an annular component which is slidable axially of the inner joint member. However, such an annular component is complex and expensive to manufacture, and it is difficult to obtain the required range of movement thereof relative to the inner joint member.